Psoriasis

Psoriasis is a distressing life-long skin disease. In mild cases, there may be a few patches of red raised skin covered by a variable build up of white scales (called plaques) on the elbows, knees or scalp. But severe psoriasis can lead to thick scaly skin over large parts of the body. In some people, psoriasis also attacks the joints and may lead to mobility problems.

Psoriasis affects between 1 in 200 and 5 in 100 people, depending on what country they live in. More than twice as many white people have it as black people.

In psoriasis, the normal cycle of growth and death of skin cells is disturbed. Skin cells multiply too fast and don’t grow properly. Instead, they pile up on the surface.

Psoriasis is rarely life-threatening, but it can make people very upset and depressed about the way they look.

In recent years, scientists have discovered that a problem with an antigen of the immune system may trigger psoriasis. Immune cells called T lymphocytes appear to be activated and to move to inflamed areas of skin and release chemicals that make the cells multiply too quickly and inefficiently.

Understanding more about these mechanisms, and the genes which may make some people more likely to get psoriasis, is helping in the development of new treatments.

Treating psoriasis

Mild cases of psoriasis are treated with creams that lubricate the skin and make it more comfortable. Other creams aim to slow down the production of skin cells, so there is less scaliness, but some are rather messy or irritate the skin.

Medicines that are similar to vitamin D can also slow down the turnover of skin cells. Another option is to use a steroid cream to make the skin less inflamed.

For more severe cases, phototherapy can reduce over-production of skin cells. A drug called a psoralen can be taken and then activated by ultraviolet light (UV-A) to help reduce skin cell turnover. But a lot of sessions may be needed, there are few treatment centres and there is a small risk that the UV-A may cause skin cancer.

In the last decade, doctors have treated severe psoriasis with medicines that are used to prevent transplanted organs from being rejected. They work by suppressing the activity of some of the immune cells that trigger psoriasis, but they have unwanted effects too.

Now, research is looking for better ways to block the immune cells that are involved in psoriasis without harming other parts of the body.